Native implementation of Bluebird's Promise.props with flow annotation

gistfile1.txt

function props<A, O: { [key: string]: A }>(promises: O): Promise<$ObjMap<O, typeof $await>> {
  const objMapping: {[number]: string} = {};
        
  return Promise
    .all(Object.keys(promises).map((key: string, index: number) => {
      objMapping[index] = key;
    
      return promises[key];
    }))
    .then(fulfilledArray => {
      return fulfilledArray.reduce((result, value, index: number) => {
        result[objMapping[index]] = value;
        
        return result;
      }, {});
    });
}